in order for people to extend the GeoExt.data.LayerModel, we need to use inheritableStatics for the static function and we need to make sure that inside of the static function createFromLayer we access a static function i.e. getProxy instead of the member proxy
Merge pull request #203 from bartvde/layermodel

in order for people to extend the GeoExt.data.LayerModel, we need to use... (r=@juliensam)